This invention relates to electrical connectors, and more particularly to an improved head for such connectors and a method of securing a wire to the improved head.
Electrical connectors, as commonly constructed, include a head that can be connected to a first electrically conductive material such as a wire and a base that can be connected to a second electrically conductive material such as a second wire or a metal plate. There are a variety of uses for such connectors. For example, electrical connectors are often used in electric resistance heaters to connect a heating element to an outside source of electrical energy. Frequently, the head of an electrical connector has a generally semi-spherical shape with the surface of the top of the head defining a slot or groove. An electric wire can be mechanically bonded or secured to such a head by inserting one end of the wire into the slot and then tacking or staking the end of the wire to the head. The stacking process includes, typically, centering the head under a riveter and then hammering, or peening, the center top of the head in a downward direction. The hammering flattens the top of the head. That is, material at the very top of the head on either side of the slot is forced downward and is spread out. This causes the material to move over the wire in the slot. If a sufficient amount of material is moved over the wire, the wire becomes bound to the head and is prevented from moving from the slot. After the wire has been staked to the head, the electrical connection between the wire and the head can be improved by spot welding the wire to the head.
With the above described staking process, the hammering force is in a downward or vertical direction, while the material at the top of the head must move in a horizontal direction in order to move into the slot over the wire. This results in a relatively large peening force being needed to move a comparatively small amount of material over the wire. Also, since good results can be obtained if an approximately equal amount of material from either side of the slot is forced over the wire, it is desirable that the peening force be accurately directed so that it is distributed about equally to the material on either side of the slot.
The above described staking process has several disadvantages. First, because of the size and accuracy required of the peening force, it is difficult to obtain the correct force, and the proper force is not always applied. If the force is inadequate or not properly directed, then the wire may not be securely staked to the head and the wire may break away from the electrical connector. A weak stake also may cause a weak spot weld, and this results in poor electrical contact between the wire and the head. A second disadvantage is that only a relatively narrow range of sizes of wires can be staked to any one size of head. This is due to the fact that if the cross-section of the wire is considerably smaller than the cross-section of the slot, then a substantial amount of matter must be forced into the slot to prevent the wire from being removed from the slot. The size of the peening force needed to move this amount of matter may be so large that when applied it will actually break the head. Or, the force may be beyond the capability of the riveting machine.